Fume hoods which are equipped with sashes conventionally include sash counterbalances to facilitate raising and lowering the sash and to maintain the sash in the desired position. A typical sash counterbalance arrangement includes two sash weights which are concealed within opposite front corners of the fume hood and connected to the sash by cables which are routed over pulleys at the top of the hood. Such sash weights often bump and scrape inside surfaces of the fume hood as the sash is raised or lowered, causing irritating noises. Further, if one of the connecting cables breaks, the remaining single sash weight is insufficient to balance the weight of the sash, and the sash drops.
At least one fume hood uses a single sash weight concealed in a front corner post which is connected to both sides of the sash by cables. If one of the cables breaks, the counter-balance is maintained. However, the sash weight can still bump and scrape the inside of the corner post as it moves up and down.